27 



almost completely dissolved and our bit of paper again quite 

 red. If it is a mineral superphosphate there will remain some 

 phosphate of iron undissolved in the acetic acid, but if it is a 

 pure bone the acetic acid will make it quite clear again. Fill 

 the flask up to the mark with cold water, mix thoroughly bv 

 shaking, and put it on one side till the phosphate of iron has 

 all settled at the bottom. The upper portion of the solution 

 havmg now become quite clear, it is ready for the completion 

 of the analysis. Take the pipette which holds fifty decems,. 

 and which should be quite dry and clean or else be rinsed out 

 with a little of the solution, insert the point in the solution, but 

 be careful not to stir up the deposit, and draw it full with the 

 mouth, then immediately place a wet finger on to the top so as 

 to close the aperture, thengradually lower the solution admitting- 

 a little air till the fluid is down to the mark on the neck. 

 Remove the pipette full of the solution to the small flask, take 

 the finger away and let it empty into the flask, blow out the 

 last drop, and add five decems of the acetic mixture to the 

 little flask. 



Now light the spirit lamp, and place it under one of the 

 rmgs of the retort stand, which should be lowered down to the 

 flame, on the top place the small piece of wire gause and on 

 this the small flask, and let the contents almost boil. 



While this is doing get the burette, and if it is quite dry fix 

 It in the burette holder and fill it with the Uranium solution, then 

 lower the solution till the bottom part of the curve which the 

 solution makes is just level with the or Zero line on the 

 burette. If the burette is not dry wipe it out with a stick 

 with a bit of rag on the end, and then rinse it out with 

 two or three decems of the Uranium solution and throw them 

 away. 



The burette now being ready, and the solution hot, let a few 

 decems run into it and stir well with the glass rod It will 

 generally be safe to let 10 decems run in at once, then take out 

 a drop with the glass rod, put it on a white surface such as the 

 bottom of a dinner plate and push into it a little of the Ferro- 

 Cyanide of Potassium powder with the other end of the rod • no 

 chnage should take place. If a deep chocolate colour should 

 appear the superphosphate is a very poor one, and another 5a 

 decems of the solution must be taken out, heated and treated as 

 before, running in fewer decems of the Uranium at first 



We will suppose that no colour was given on first 'testing 

 then keep on running into the flask Uranium solution one decern 

 at a time testing with Ferro-Cyanide after each addition, and 

 occasionly warming the flask till at last a chocolate colour is- 

 given, then note down how many decems have been used This 

 first titration is a good guide as to the quantity which will be 

 required in the next, which is to be the exact one. 



We will suppose that a deep colour was given when we had 

 used 16 decems. Now empty the little flask, rinse it out, and 



